Arc electrode, especially for vacuum switches

ABSTRACT

An arc electrode, especially for vacuum switches, comprising two oppositely situated electrodes for taking-up the base points of the arcs and formed of a number of plates. The narrow surfaces of the plates are disposed to confront the oppositely situated electrodes. Gaps or spaces are maintained free between the individual plates, the width of such gaps being at least equal to the thickness of a plate.

United States Patent Amsler Nov. 20, 1973 ARC ELECTRODE, ESPECIALLY FOR3,261,954 7/1966 Yonkers zoo 144 B VACUUM SWITCHES FOREIGN PATENTS ORAPPLICATIONS lnvemori Joachim Amslel, Umeremfelde", 451,286 5/1968Switzerland 200/144 B Switzerland 7 Xs sig ne ei Sprecher & Schuh A G,Aarau, Primary ExaminerRobert S. Macon Switzerland AttorneyEric H.Waters et al. 22 Filed: Mar. 7, 1972 21 Appl. No.: 232,480 [571 ABSTRACTAn arc electrode, especially for vacuum switches, comprising twooppositely situated electrodes for tak- [30] Foreign Applufatlon PnomyDam ing-up the base points of the arcs and formed of a Oct. 8, 1971Switzerland 14702/71 number of plates The narrow Surfaces of the platesare disposed to confront the oppositely situated elec- [52] U.S. Cl.200/144 B, 200/166 BH trodes Gaps or Spaces are maintained free between[51] hit. Cl. H01]! the individual plates, the width of h g p being at[58] Field of Search 200/144 B, 166 BH least equal to the thickness of aplate y [56] References Cited 7 Claims, 6 Drawing Figures UNITED STATESPATENTS 3,210,505 10/1965 Porter 200/144 B PATENIEDnuvzo I915 SHEET 10F2 Fig. 1

Fig. 2

PATENTEDHUV 20 I975 SHEET 2 GF 2 Fig3 Fig.4

ARC ELECTRODE, ESPECIALLY FOR VACUUM SWITCHES BACKGROUND OF THEINVENTION The present invention relates to a new and improvedconstruction of arc electrode, especially for vacuum switches, which isof the type incorporating two oppositely situated electrodes formed of aplurality of plates and destined to take-up the arc base points, thenarrow surfaces of the plates confronting the oppositely situatedelectrodes.

A contact mechanism, especially for vacuum switches, is known to the artwherein each switching element or piece is enclosed by an arc electrode.With this arrangement the arc electrode is composed of involute-shapedflexed plates disposed parallel to the axis of the switching element,the plates being assembled together into a rigid package and theseplates alternately consist of two materials of different electricalconductivity. The infeed of current to the base points of the aredisplaced radially outwardly at the arc electrode,

preferably occurs at the plates possessing the better electricalconductivity so that the thus produced arcshaped current paths exert atangential acceleration force upon the arc. As a result the arc rotatesat the outer periphery of the arc electrode about the contact axis untilit is extinguished. Owing to the rapid movement of the base points ofthe arc there is prevented an undesired, high local heating of thecontact surfaces. A drawback with this arrangement is that for cut-offor interruption currents exceeding about l0 kA the contact burn-off isrelatively great so that the longevity of the vacuum switch is reducedfor high cut-off currents.

Experiments have shown that the arc between largesurface electrodes,such as for instance between the previously mentioned arc electrodes,can burn in two different conditions. Below SkA the arc burns in adiffuse or scattered manner. If this current boundary or limit isexceeded then there prevails a column or pillar arc. The contact bum-offfor column arcs is considerable and therefore the longevity of thevacuum switch is also reduced. A diffuse arc does not cause any twoappreciable contact burn-off. For the purpose of obtaining the diffuseregion of the arc there is known to the art a solution in which the arcburns and travels between two coaxial cylinders. A drawback of thissolution is, however, that the ionized gas during cut-off of the switchremains between both oppositely situated electrodes and it is difficultto extinguish the arc.

According to a further known proposal in the art there is provided twobowl-shaped constructed electrodes disposed in confronting arrangement,each electrode being provided with an inwardly turned or flanged lipportion bounding an opening, the openings of the bowl-shaped electrodesconfronting one another. With this proposal the ionized gas from thespace between the electrodes is collected in the spaces of thebowl-shaped electrodes which are not electrically loaded, cooled andcondensed. A drawback of this arrangement is that between thebowl-shaped electrodes there also appears a column arc when exceedingapproximately kA cut-off currents, bringing about marked contactburn-off.

SUMMARY OF THE INVENTION Hence, from what has been discussed above itwill be recognized that the technology in this particular field is stillin need of an arc electrode, especially for vacuum switches, which isnot associated with the aforementioned drawbacks and limitations of theprior art proposals. It is therefore a primary object of the presentinvention to fulfill the existing need in the art.

Another and more specific object of the present invention relates to anew and improved construction of arc electrode rendering possiblemaintenance of the diffuse range of the arc also when exceedingapproximately 5 l0 kA cut-ofi current values.

Now, in order to implement these and still further objects of theinvention, which will become more readily apparent as the descriptionproceeds, the invention contemplates leaving spaces or gaps free betweenthe individual plates, the width of such spaces or gaps being at leastequal to the thickness of a plate. A particularly advantageousarrangement of the plates is then realized if the plates are radiallyarranged about an axis common to both oppositely situated electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be betterunderstood and objects other than those set forth above, will becomeapparent when consideration is given to the following detaileddescription thereof. Such description makes reference to the annexeddrawings wherein:

FIG. 1 is a longitudinal sectional view through a preferredconstructional form of inventive vacuum switch embodying the teachingsof this development;

FIG. 2 is a transverse cross-sectional view taken through the center ofthe vacuum switch depicted in FIG. 1, taken substantially along the lineIIII thereof;

FIG. 3 illustrates details of an electrode construction consisting ofparallel plates;

FIG. 4 illustrates details of an electrode construction consisting ofcoaxial cylinders;

FIG. 5 illustrates details of an electrode construction formed of flexedor angled plates; and

FIG. 6 schematically illustrates a portion of the surface of anelectrode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to thedrawings, in the illustration of the exemplary embodiment of vacuumswitch as depicted in FIG. 1, the vacuum tight or sealed housing of theswitch consists of a cylindrical portion 1 formed of electricallyinsulating material, a metallic cover member 2 with the switchingelement or piece 3 fixedly seated therein and the tubular-shapedelecrode support or carrier 4 mounted thereon, and a second metalliccover member 5 which carries a switching element or piece 7 and theelectrode support 8, the switching element 7 being secured so as to bemovable via a diaphragm or bellows 6 with the metallic cover member 5.The movable switching element 7 has been illustrated in its switching-inor connection position and can be moved to-and-fro in the direction ofthe arrow by means of any suitable and therefore non-illustratedactuation mechanism. The electrode supports 4 and 8 carry the radiallyarranged plates 9 and 10 of the arc electrode. In this connectionreference should also be made to FIG. 2. The inner surface of thecylindrical portion 1 is protected against condensation of the metalvapors which are present by means of a tubularshaped metal shield 11which is only secured to the center of the cylindrical part 1 and thuscompletely insulated from both metallic cover members 2 and 5.

The switching elements or pieces 3 and 7 possess a truncated or bluntcontact support surface 12. During disconnection of the current theswitching elements 3 and 7 separate and the are initially burnstherebetween. The base points of the are then wander over to the plates9 and 10, wherein the delivery of current occurs by means of bothelectrode supports 4 and 8. The are burning between the electrodesformed of the plates arranged so as to have therebetween intermediatecompartments or spaces is practically not able to build-up an axialpressure of force because the axially accelerated ionized gases in thespaces between the plates arrives at a compartment or space which is notelectrically loaded. The hot gases flowing through the spaces betweenthe plates 9 and 10 are cooled and condensed.

The are burns in a diffuse or scattered manner between the inventivelyconstructed electrodes up to very large values of the cut-off orinterruption current, considerably exceeding 5 kA. The gaps or spacesformed between the plates 9 and 10 and the very narrow surfaces of theplates 9 and 10 confronting the opposed electrodes prevent the formationof column arcs and therefore increase the longevity of the vacuumswitch.

Now as best seen by referring to FIG. 3 it should be recognized that theoppositely situated electrodes could also be formed of parallellyarmaged plates 13. As is to be further understood the plates 13 of thearrangement of FIG. 3 are inserted into slots 14a of the electrodesupport 14 and welded or riveted thereat.

In FIG. 4 there is shown a further construction of the electrodeswherein the latter are assembled together from concentric cylinders 15secured to electrode supports 16.

In the arrangement of FIG. 5 the flexed or angled plates 18 and 19,which are situated parallel to the axis 17 (FIG. 1) which is common toboth oppositely situated electrodes, are mounted at the electrodesupport 4. This construction also brings about a tangential accelerationof the burning are between the electrodes.

An essential criteria for maintaining a diffuse are between theelectrodes consisting of adjacently arranged plates with freeintermediate spaces therebetween concerns the sum of the length of theedges appearing at one square centimeter of electrode surface.Experience has shown that the sum of the edge length should at leastamount to 3 cm. per square centimeter of electrode surface. In FIG. 6there is illustrated an embodiment wherein the sum of the edge lengthsof the plates 20, 21 and 22 amounts to 6 cm. for a square centimeter ofelectrode surface.

The diffuse are not only has its arc projection surface at the narrowsurfaces of the plates confronting the oppositely situated electrodes,rather also at the wide surfaces of the plates bounding the spaces orgaps between the plates. In order to maintain the difiuse region of theare for cut-off currents exceeding 5 l0 kA experience has shown that thedimensions 23 (FIG. 1) of the plates below the narrow surfacesconfronting the oppositely situated electrodes must amount to at least 1cm.

The use of the inventively constructed arc electrodes is not solelylimited to merely vacuum switches, although such constitutes aparticularly useful environment. 7

While there is shown and described present preferred embodiments of theinvention, it is to be distinctly understood that the invention is notlimited thereto but may be otherwise variously embodied and practicedwithin the scope of the following claims. Accordingly,

What is claimed is:

1. An arc electrode arrangement particularly for vacuum switches,comprising two oppositely located electrode rods, arcing means for eachelectrode rod and having a plurality of plates separated from another bygaps therebetween, said plates extending substantially parallel to theaxis of the respective electrode rod, said arcing means having an arcingface defined by edges of the plates to take up the base points of thearc, the width of said gaps being at least equal to the thickness of aplate.

2. The are electrode as defined in claim 1, wherein the plates arerotationally symmetrically arranged about an axis common to bothoppositely situated electrode rods.

3. The are electrode as defined in claim 2, wherein the plates areradially arranged about an axis common to both oppositely situatedelectrode rods.

4. The arc electrode as defined in claim 1, wherein the plates areflexed and parallelly arranged with regard to an axis common to bothoppositely situated electrode rods.

5. The are electrode as defined in claim 1, wherein the plates arearranged in substantially parallel planes.

6. The arc electrode as defined in claim 1, wherein the sum of thelength of the edges of the plates at the electrode surfaces confrontingthe oppositely located electrode rods amounts to at least 3 cm. persquare centimeter. v

7. The are electrode as defined in claim 1, wherein the dimensions ofthe plates below said plate edges confronting the oppositely locatedelectrode rods amounts to at least one centimeter.

1. An arc electrode arrangement particularly for vacuum switches,comprising two oppositely located electrode rods, arcing means for eachelectrode rod and having a plurality of plates separated from another bygaps therebetween, said plates extending substantially parallel to theaxis of the respective electrode rod, said arcing means having an arcingface defined by edges of the plates to take up the base points of thearc, the width of said gaps being at least equal to the thickness of aplate.
 2. The arc electrode as defined in claim 1, wherein the platesare rotationally symmetrically arranged about an axis common to bothoppositely situated electrode rods.
 3. The arc electrode as defined inclaim 2, wherein the plates are radially arranged about an axis commonto both oppositely situated electrode rods.
 4. The arc electrode asdefined in claim 1, wherein the plates are flexed and parallellyarranged with regard to an axis common to both oppositely situatedelectrode rods.
 5. The arc electrode as defined in claim 1, wherein theplates are arranged in substantially parallel planes.
 6. The arcelectrode as defined in claim 1, wherein the sum of the length of theedges of the plates at the electrode surfaces confronting the oppositelylocated electrode rods amounts to at least 3 cm. per square centimeter.7. The arc electrode as defined in claim 1, wherein the dimensions ofthe plates below said plate edges confronting the oppositely locatedelectrode rods amounts to at least one centimeter.